Merged DDWFTTW in a “Real” Wind

[profpangloss]

You ask how "anyone" can claim the cart went DDW, but sadly for your agenda it is not just anyone who is claiming it. It is the worlds foremost authority on landsailing. It is the world record holder who before he educated himself believed ddwfttw was impossible. It is the folks who know that millisecond transients in wind direction cannot provide a tacking force to a cart with a sail never mind to one without. It is the folks who know that, although they are the best at what they do, they themselves could not even begin to duplicate the BB's performance in the same wind conditions.

NALSA only has experience with speed records and have NEVER conducted any tests where the relative directions of the craft to the wind was of any importance. They have ZERO experience with DDW and this was their FIRST attempt at measuring such. It is obvious from the data that they screwed up, big time. Just LOOK AT THE CHARTS! The evidence is right in front of you and it is right in front of everyone else. This record will be retracted, if NALSA hopes to retain any credibility. Argue all you want, but the evidence does not support you or this unqualified claim of DDW.

 

[Llyricist]

This is the original NALSA data? I am not surprised! How does this factor into the claim the cart went DDW? I have seen a figure of 4 degrees off of DDW, where did that come from? From this chart, what is the RMS deviation from DDW? I will calculate it myself, but I would like to see other people do it as well. Just looking at the chart I'd say the RMS devaition is about 20 degrees. How can anyone seriously claim the cart went DDW? I will post more on this later!

Way to out yourself there.

But beyond that ludicrous use of RMS that only two people in the world advocate, presumably because it yields a larger number, is the fact that ~60% of that chart is entirely irrelevant, having occurred after the record's test period. And the rest of the data clearly shows the cart's performance is significantly downgraded during that time.

Also, why is he showing the raw wind direction? It is not relevant, what is relevant is the deviation of the cart from that direction. While that chart looks very similar, it IS different.

During the 10 second test period that set the parameters of the record run, the cart averaged 4.1 degrees off DDW. And for at least 3 seconds during that 10 seconds, was less than 1 degree off DDW, and accelerating the whole time, in fact, its acceleration was increasing during that DDW period.

Here's a clue before you go the route I can imagine you will take, you can't coast and accelerate at the same time.

 

[humber]

This is the original NALSA data? I am not surprised! How does this factor into the claim the cart went DDW? I have seen a figure of 4 degrees off of DDW, where did that come from? From this chart, what is the RMS deviation from DDW? I will calculate it myself, but I would like to see other people do it as well. Just looking at the chart I'd say the RMS devaition is about 20 degrees. How can anyone seriously claim the cart went DDW? I will post more on this later!

That is the raw true wind data, as calculated from the vane and wind speed by NALSA for the run and some time either side of it. It makes no real difference as to how that relates to the cart heading, because the cart asymmetrical. The wind speed is not accurate because the anemometer is too slow to record short gusts.

I have not yet calculated much, or worked the raw vane data. There are many runs, not just the record run.

The previous 4 degrees, refers only to the 10 second measurement period where the 50 samples are averaged as the arithmetic mean.
That is then compared to the fixed course of the cart, to yield 4 degrees.
The RMS true wind, is 15 or perhaps 11 degrees for that same period.

 

[Llyricist]

What I find most nauseating at the moment are your posts.

A. It matters not what you or anyone else tells me. All that matters is what the chart tells me.

That chart does not tell you much that is relevant.

B. RMS is the ONLY correct way to calculate wind power. You should learn about it.

No, you should. The only time RMS is used in relation to air movement is in calculating the kinetic energy of the molecules in order to determine temperature the hard way.

C. What part of the chart is the test period and what part is not?

The part centered at about 393 as labeled on that chart, do yourself a favor and look at the reports on the NALSA site.

D. If the cart was not at 0 degrees, what was the reference for the wind direction and at what angle was the cart?

The reference angle was 0 at due east, +90 north, -90 South. The cart varied between -2 and -5 degrees during the time leading up to and including the test period.

How do you determine the cart averaged 4 degrees off of the wind when the wind was changing direction the way the chart indicates?

by averaging the deviation from DDW during the 10 second test period.

The cart could not have been tracking those changes as it held to a steady course. The cart was tacking the wind. Do you find that nauseating?

There is no mechanism on the cart capable of tacking the wind...... except the propeller blades.

 

[jduffy77]

That is the raw true wind data, as calculated from the vane and wind speed by NALSA for the run and some time either side of it. It makes no real difference as to how that relates to the cart heading, because the cart asymmetrical.

^^^^ LOL, please stop Humber its just too funny now.

 

[Subduction Zone]

ppg has a very small point. This was NALSA's first attempt at testing something that was moving directly downwind. If they really wanted to test it they could have used a giant treadmill and put the cart on that. Oh wait, that would only show that the cart can go faster than the wind, not how much faster than the wind it could go. It seems that the test in a real wind is still the best for that.

 

[windgrins]

An observation to all!

A. You have been told ad nauseam that the RMS deviation was not 20 degrees.

B. You have been told ad nauseam that RMS is not the most sensible way to look at the wind.

C. You have been told ad nauseam that only the test period is relevant.

D. You have been told ad nauseam that the cart was not at 0 degrees.

It was at 0 degrees off the wind for some of the time. The cart averaged 4 degrees off the wind.

It is, or should be, obvious to anyone who has ever responded to Humber and his posse that he never, ever, sees or changes an argument once he establishes it. He flips sides many times when he realizes everyone including him thinks his viewpoint is absurd and then claims that was his viewpoint all along.

I have learned for myself that attempting a discussion with Humber is counterproductive and will never produce anything but negative results. To this end, I'm no longer responding to any quotes/taunts etc. as his only time he has ever made a point to me was to point out a trivial grammar error. It's like trying to teach a pig calculus-the pig just ignores you and you just get dirty.

Spork was absolutely correct on this one with his early prediction.

WindGrins

 

[humber]

What I find most nauseating at the moment are your posts.

I won't be temporary.

A. It matters not what you or anyone else tells me. All that matters is what the chart tells me.

Yes. It speaks volumes.

B. RMS is the ONLY correct way to calculate wind power. You should learn about it.

As if...

C. What part of the chart is the test period and what part is not?

This is the time from when the CV is stable to the end of the run + 10s.

Direct Down wind....sure it is.

D. If the cart was not at 0 degrees, what was the reference for the wind direction and at what angle was the cart?

The cart heading of 4-7 degrees. I have the vane data, but there is an unspecified offset to avoid the null of the potentiometer. I have asked for that, and a for some other missing bits. I hope to get a report together for NALSA, and let them comment on it before posting. There are a lot of failed runs, that tell a lot.
Critical, is the claim that the cart "is best" ddw, but that is not the case.
It responds to changing wind, though I suspect the prop limits and regulates that, so it is not so obvious as if the cart were more responsive. Its mass is a great leveler.

How do you determine the cart averaged 4 degrees off of the wind when the wind was changing direction the way the chart indicates? The cart could not have been tracking those changes as it held to a steady course. The cart was tacking the wind. Do you find that nauseating?

The cart is generally on a fixed heading, within GPS error margin.
The cart makes not attempt to follow the wind.

 

[humber]

NALSA only has experience with speed records and have NEVER conducted any tests where the relative directions of the craft to the wind was of any importance. They have ZERO experience with DDW and this was their FIRST attempt at measuring such. It is obvious from the data that they screwed up, big time. Just LOOK AT THE CHARTS! The evidence is right in front of you and it is right in front of everyone else. This record will be retracted, if NALSA hopes to retain any credibility. Argue all you want, but the evidence does not support you or this unqualified claim of DDW.

Lots of basic errors. The vane is too slow and so is the sampling rate.
The anemometer can't track the vane changes...etc...

 

[humber]

There is no mech....

Piffle.

 

[humber]

^^^^ LOL, please stop Humber its just too funny now.

As if you had a clue. It's game over when all that data is analyzed and huffing and puffing won't work.

 

[Modified]

I suspect people here are really arguing at cross purposes and not defining their terms precisely. There are many forms of potential energy, so just saying potential energy without a qualifier can be confusing. In this case, the balloon’s gravitational potential energy certainly increases as the balloon rises, but its buoyant potential energy is decreasing.

Right. Depending on the type of balloon, there also may be PE due to the stretching of the balloon that can be harnessed by releasing the gas, PE that may be harnessed by burning the balloon if it is flammable, and others.

If what we are talking about is the PE that can be harnessed by the pull of the balloon as it rises or falls, then a positively buoyant balloon loses PE as it rises.

 

[Llyricist]

Here's a little help for humber, in case he sees this, try 263.5 or 96.5 for the offset, depending on how you go about applying it. Don't forget to normalize the CV heading to +/- 180 instead of the 360 range it comes as.

 

[humber]

Right. Depending on the type of balloon, there also may be PE due to the stretching of the balloon that can be harnessed by releasing the gas, PE that may be harnessed by burning the balloon if it is flammable, and others.

If what we are talking about is the PE that can be harnessed by the pull of the balloon as it rises or falls, then a positively buoyant balloon loses PE as it rises.

Coz that's what Spork says. Qualified people say otherwise.

Question: How can the sum of potential energy and kinetic energy
be constant when a helium balloon moves up in air as both potential
energy and kinetic energy increases?
---------------------------------------
The potential energy is going _down_ as the balloon rises. (2) This is
counter-intuitive because the standard way of describing potential energy
is based on the assumption that gravity is much greater than the buoyancy
(buoyancy is ignored). But that is not a good assumption with the helium
balloon. Potential energy is actually stored in the submerged (in air)
helium balloon -- to help visualize, think of how much work it takes to
submerge a basketball under water. With the basketball, you are pushing
water up (it is displaced by the ball) against gravity, storing potential
energy. It works the same way with the balloon submerged in air. Filling
the balloon displaces air, thereby storing potential energy in the
balloon. When you release the balloon, that potential energy is converted
to kinetic energy (there are other factors as well -- it expands as it
rises, for example, but I will neglect those for purposes of this answer).

Hope this helps,
Burr Zimmerman

That is, the heavier air loses potential energy as it ascends, and transfers it to the balloon, so it gains KE as it rises. When it stops, or becomes NB, all of that is PE.
When the balloon is NB, the heavier air will not accelerate it (because it will not ascend, because the force of gravity is the same on the balloon as the air),
so not add KE, and the work must come from what ever raises it to height. The balloon gains PE by the work. Hence the floors of the building.

Or with the analogy with a rock. The rock has PE, which becomes KE as it falls, the buoyant balloon has KE, which becomes PE as it rises.
When NB, that exchange does not take place, and the balloon is like an imaginary sphere of air, so gains PE with height or the air could not lose PE as it decends, as the
text says it does.


================================================== ==================
The potential energy of the helium balloon increases as it ascends, (1)
but as it ascends it allows heavier air to descend to take its
place. The air's potential energy thus decreases. The decrease in
the air's potential energy is of greater magnitude than the increase
in the helium balloon's potential energy, so overall potential
energy decreases.

 

[humber]

dp

 

[humber]

Here's a little help for humber, in case he sees this, try 263.5 or 96.5 for the offset, depending on how you go about applying it. Don't forget to normalize the CV heading to +/- 180 instead of the 360 range it comes as.

263.5 or 96.5 doh.

That data is not available, so you have no idea, and it makes no difference to the calculated true wind, because NALSA used that. So that rather fixes that.

Don't forget to normalize the CV heading to +/- 180 instead of the 360 range it comes as.

Nice try, but I know the GT31 very well.
What is the 38th value of the vane data?
Calculate the wind speed change between the 40th and 41st reading, allowing for the anemometers transient response.
Spork channel is corrupted and he won't know what hit him.

 

[69dodge]

Check my diagram. It shows the theoretical max speed (no losses), realistic speed (with losses) and initial acceleration, as functions of the vehicle advance ratio.

[qimg]http://i54.tinypic.com/2gv0kew.png[/qimg]

Can you say something about how you calculated the realistic speed with losses?

(I understand the theoretical max speed without losses.)

 

[profpangloss]

But beyond that ludicrous use of RMS that only two people in the world advocate, presumably because it yields a larger number, is the fact that ~60% of that chart is entirely irrelevant, having occurred after the record's test period. And the rest of the data clearly shows the cart's performance is significantly downgraded during that time.

I hope you are not serious! Wind power is usually associated with wind turbines, not propellers (cough) and the turbines are designed to orient themselves so they are facing directly into the wind. That being the case, it is not necessary to consider RMS wind direction. But if you think it is ludicrous to consider it when the turbine, or in this case the propeller (chuckle) is not always aligned with the wind, than you are quite mistaken. In the case of varying wind direction, the wind power density depends as much on RMS wind direction as it does on velocity and the velocity in varying wind conditions is also calculated as an RMS value. Do you think only two people in the world advocate RMS wind calculations? Then which one of those two wrote this research paper?

http://www.gsmt.noao.edu/studies/wind_tests4/wprv_all.htm

Furthermore, a propeller is the antithesis to a turbine. Think about that for a moment. If the turbine works best when it is aligned with the wind direction, doesn't that indicate the propeller will work worst when similarly aligned? I think it is obvious that if a propeller is used to gather wind energy, it will do it best when it is not aligned with the wind direction. It only requires common sense to see that, but I'm sure I can find some supporting mathematics as well.

 

[Llyricist]

263.5 or 96.5 doh.

That data is not available, so you have no idea, and it makes no difference to the calculated true wind, because NALSA used that. So that rather fixes that.

Actually, I do have a way of knowing that. It is the figure they used, I know that because I got the same results they did when I used it.

Nice try, but I know the GT31 very well.

It has nothing at all to do with what GPS was used, it has to do with using the same convention for all the data.

What is the 38th value of the vane data?

Give a time reference, in my data it's 264.4 @ Time reference: 588967.4

Calculate the wind speed change between the 40th and 41st reading,

The measured change was .07973 MPH from 588967.8 to 588968 I don't know where your baseline is, so without the time reference, your 40th and 41st may be different.

allowing for the anemometers transient response.

The actual change may be different by some small amount but is irrelevant.

 

[69dodge]

[...] turbines are designed to orient themselves so they are facing directly into the wind. [...] Furthermore, a propeller is the antithesis to a turbine. Think about that for a moment. If the turbine works best when it is aligned with the wind direction, doesn't that indicate the propeller will work worst when similarly aligned?

What's the opposite of facing directly into the wind? Facing perpendicular to the wind, or standing with one's back to the wind?